‘Awfa messy eaters’: scientists solve the mystery o whan black holes ‘burp’

Scientists hae solveit the mystery o whan black holes burp, whan these astronomical bodies launch jets efter feedin on stars, blastin material enourmous distances intae space. Black holes are objects sae densely compact that ayont a certain point their gravity is ower strang for licht an matter tae escape. This mairch o nae return is kent as the event horizon, the point at whilk escapin wad require somethin tae traivel faster than the speed o licht.

Despit their reputation as cosmic sinkholes, black holes are actually verra messy eaters, said Dr Adelle Goodwin, an astrophysicist at Curtin University in Wastren Australie. Ye hae tae get verra, verra close tae a black hole tae reach the event horizon, Goodwin, wha is a Forrest Research Foundation fellow, said. Stars get destroyed forder oot than that.

Scientists ken frae rare observations o stars bein torn apart by black holes, a process that involves a stretchin effect kent as spaghettification, that only aboot half o the star that gets ower close tae the black hole will end up eventually bein swallied by that black hole, Goodwin said. The ither material is launched back intae space in pouerful jets an ootflows, whiles sae lairge that they can influence the entire evolution o a galaxy, she said. Ye can think o it as a black hole burp.

But the timin o these burps hid previously been mysterious tae astrophysicists. Whiles it wad happen a year efter the black hole destroyed the star, whiles it wad happen three or five years efter. In new research publisht in the journal Nature Astronomy, Goodwin an co-author Dr Andrew Mummery frae the Institute for Advanced Study believe they hae fund the answer, usin radio telescopes tae study 20 tidal disruption events, instances whaur stars are eaten by supermassive black holes. Radio is the only frequency whaur we can watch the jets an ootflows as they are movin ootwards, Goodwin said.

They fund that supermassive black holes, whilk range in size frae hunners o thoosands tae billions o times the mass o oor sun, fire aff pouerful jets in twa distinct phases in their feedin cycle. The first occurs whan the black hole is feedin at verra heich rates. The second occurs hunners tae thoosands o days efter the star is first torn apart, whan the feedin rate draps tae aboot 2% o the maximum rate at whilk a black hole can swallow material. That same threshold is already kent tae trigger burps frae stellar-mass black holes, much smawer bodies aboot 10 tae 50 times the mass o oor sun.

The research showit that black holes appeared tae release jets at the same point in their feedin cycle regairdless o size, Goodwin said. She said the findin wad enable scientists tae precisely predict whan sic jets wad be released, narrowin observation windaes an freein up precious telescope time. She addit: We can really start tae unnerstand no just whan the jets are launched, but also how strang they are an if that is syne dependent on the black hole properties.

Dr Sara Webb, an astrophysicist at Swinburne University wha wasna involved in the research, said: We are still tryin tae untangle the verra fundamentals o the maist extreme objects in the universe, supermassive black holes. Webb said the study showit that supermassive black holes behave rather predictably at twa distinct periods in their evolution an the researchers had tied this back tae what we hae seen previously on the much smawer scale stellar-mass black holes.